1. Field of the Invention
The present invention relates to a self-propelled compaction roller of the kind used in road construction, for example, in order to compact the earth underneath a roadway and also to compact the construction material of a roadway. Compaction rollers of this kind generally comprise a drive system having a drive assembly designed as a diesel engine, for example. This drive assembly drives a hydrostatic/mechanical driving unit, the latter comprising a hydraulic pump and a hydraulic motor, for example. The energy fed into the hydraulic motor in this driving unit in the form of a flow of pressurized fluid is converted in said hydraulic motor into kinetic energy for the travel drive and, if appropriate, also for an oscillator or vibrator.
2. Background of the Related Art
DE 10 2006 060 014 B4 discloses a hydrostatic drive in which recovery of braking energy is provided in order to obtain efficient use of energy. For this purpose, an energy storage unit is integrated into the hydrostatic/mechanical transmission arrangement, i.e. into the circuit for the flow of pressurized fluid between the hydraulic pump and the hydraulic motor. In the overrun state, that is to say when a drive assembly driving the hydraulic pump is not being operated for the purpose of outputting a driving torque but is being used to support a braking torque, the hydraulic motor operates as a pump and charges a pressurized fluid accumulator of the energy storage unit. In the traction state, that is to say when a driving torque is being provided by a drive assembly in order to drive the hydraulic pump, the energy thus stored in the overrun state is fed into the pressurized fluid circuit between the hydraulic pump and the hydraulic motor in order to provide support.
DE 10 2006 046 127 A1 discloses a drive system having a hydrostatic/mechanical transmission arrangement, in which the drive shaft of a diesel internal combustion engine acting as a drive assembly drives both a hydraulic pump and, via a gear stage, the hydrostatic/mechanical transmission arrangement. Together with the hydraulic pump of the hydrostatic/mechanical transmission arrangement, a hydraulic pump/motor unit is driven, which can be varied between a pump mode and a motor mode and, in the pump mode, charges a pressurized fluid accumulator and, in the motor mode, drives the hydraulic pump of the hydraulic/mechanical transmission arrangement via a mechanical interface in parallel with the driving torque supplied by the diesel internal combustion engine.
DE 10 2008 015 729 A1 discloses a drive system in which the driving torque provided by a diesel engine is transmitted to driven wheels via a mechanical transmission. A hydraulic pump/motor unit for charging a pressurized fluid accumulator in the pumping mode is operated via a power takeoff shaft of the transmission. In the motor mode, a supporting torque can be introduced into the power takeoff shaft of the transmission by withdrawing energy stored in the pressurized fluid accumulator by means of the hydraulic pump/motor unit.